White oils are essentially colorless. White oils may be either technical or medicinal grade. Technical white oils have a Saybolt color by ASTM D 156-02 of greater than +20. Medicinal grade white oils have a Saybolt color of greater than +25, more particularly equal to +30. Medicinal and technical white oil specifications require that the products have a low UV absorbance at different UV spectral ranges, as defined in FDA 178.3620 and FDA 178.3620. Medicinal grade white oils for use in food applications are required to have a kinematic viscosity at 100 degrees C. greater than 8.5 cSt and a 5 wt % boiling point greater than 391 degrees C.
White oils have high commercial value but generally are expensive to produce since they require a number of process steps including hydrocracking, high pressure hydrogen treatment, and treating by an adsorbent or a solvent. There is an incentive to produce oils which meet white oil specifications at lower processing cost. What is desired are processes not requiring hydrocracking, which will produce high quality technical and medicinal grade white oils in high yield. The desired processes would also reduce costs by requiring a lower hydrogen partial pressure for hydroisomerization dewaxing, and having a reduced number of process steps. What is also desired is a composition of white oil with high viscosity index, desired composition of molecules with cycloparaffin functionality, and low pour point, such that it may be used in a wide variety of applications.
The present invention provides solutions to shortcomings in the prior art, where white oils are either made using process steps that significantly reduce the yield of white oils that are produced out of waxy feed, utilize hydroisomerization dewaxing catalysts having low selectivity and activity, or require significant processing after catalytic dewaxing. Examples of processes that require hydrocracking prior to catalytic dewaxing, which would reduce the yield of white oils produced from a waxy feed are described in WO2004/000975, EP1382639A1, EP1366137, EP1366134, EP876446, WO200181508A1, WO200027950A1. Examples of processes that did not recognize the benefits associated with the use of highly selective and active hydroisomerization dewaxing catalysts under low hydrogen partial pressure to produce white oils at high yield without extensive processing after catalytic dewaxing are described in U.S. patent application Ser. Nos. 10/744,870 and 10/747,152, and U.S. Pat. No. 6,602,402. Other processes, such as U.S. 20040004021A1, teach how to make white oils with high viscosity indexes, but they are not appropriate when using waxy feeds having greater than 45 wt % n-paraffins and having very low sulfur and nitrogen; and/or the processes are not optimized to produce high yields of white oil from waxy feed.